The present invention relates generally to airflow intake modulation associated with aircraft engines. More particularly, the present invention relates to a mechanical system and method that modulates airflow in an aircraft inlet diffuser that is used in conjunction with an aircraft engine that integrates both a center turbine engine and a constant volume combustor (“CVC”) or ramjet arrangement with intakes formed co-centrically about the turbine. The airflow modulation directs airflow to each engine system separately and to both in combination to allow the aircraft to operate in multiple modes at different airspeeds.
The aircraft industry has desired the development of hypersonic aircraft that can takeoff and land at conventional airfields. To facilitate the design of such an aircraft, duel or integrated aircraft engines have been incorporated into the aircraft that utilize turbo jet propulsion during takeoff and landing and at air speeds of zero to Mach 2-3. Above Mach 2-3, a CVC such as a continuous detonation engine (“CDE”) or a pulse detonation engine (“PDE”) is used to maintain hypersonic speed. Likewise a ramjet type engine may be used at the higher speeds. As such, at the upper limit speed of the turbo jet, such an aircraft is designed to transition to CVC or ramjet propulsion to maintain hypersonic air speeds, and then to transition back to the turbo jet engine, when the speed goes below Mach 2-3. The use of multiple engine types on a single aircraft creates many design difficulties for the aircraft. Prior designs required separate flow paths leading to each engine to facilitate operation of the engines and has resulted in unwanted increased weight, complexity and cost.
Further, attempts to integrate different types of engines into a single structure to produce hybrid engines may result in the reduced efficiency and speed. For example, in the SR-71 Blackbird J58 engine, Pratt & Whitney, West Palm Beach, Fla. variable geometry was used to bypass flow after the fourth stage of the compressor to outer combustors that operated similar to a ramjet. Because the modified ramjet was integrated within the structure turbojet, the J58 engine could only achieve a top speed of approximately Mach 3, well below the capacity of a conventional ramjet.
In order to address some of the design difficulties associated with hybrid engines and multiple engine systems, prior designs integrated a turbo jet engine or CVC engine(s) into the aircraft structure to share a common airstream. The airflow management of the airstream in such designs is critical to the efficient and stable operation of the integrated engines. In an example of a previous airflow management system, a moveable member within the airstream inlet acts as a simple airflow shutoff for either directing airflow into the turbine or directing airflow into the CVC engines. While previous airflow management systems allow for immediate transitioning between integrated engines, such prior designs do not provide for airflow management that includes articulation to provide modified airflow during transition speeds, or to allow both engines to operate simultaneously in a designed duel engine mode.
As such, there is a great need in the art for an aircraft engine airflow management system that provides a smooth transition between operation of the turbo jet engine to a hypersonic engine by allowing both integrated engines to operate simultaneously in an intermediate speed mode.